platform/x86: intel-hid: fix _DSM function index handling

According to the ACPI spec 9.1.1 _DSM (Device Specific Method),
intel_hid_dsm_fn_mask, acquired from function index 0, is "a buffer
containing one bit for each function index". When validitaing fn_index,
it should be compared with corresponding bit.

This buffer is usually longer than a byte. Depending on whether
INTEL_HID_DSM_HEBC_V2_FN exist, it could be either
"Buffer (0x02) { 0xFF, 0x01 }" or "Buffer (0x02) { 0xFF, 0x03 }".
Probably it won't grow larger according to the description. On older
platforms, available functions could be fewer or not supported at all,
i.e., "Buffer (One) { 0x00 }".
Signed-off-by: Zhen Gong <zhengong@usc.edu>
Link: https://lore.kernel.org/r/CAJCLVRCyp0ASdWTx-PxsrDC9zFBPw0U2AtPip+_Hpj2r5gUPwA@mail.gmail.comSigned-off-by: Hans de Goede <hdegoede@redhat.com>

drivers/platform/x86/intel-hid.c

@@ -141,7 +141,7 @@ static bool intel_hid_execute_method(acpi_handle handle,
 
 	method_name = (char *)intel_hid_dsm_fn_to_method[fn_index];
 
-	if (!(intel_hid_dsm_fn_mask & fn_index))
+	if (!(intel_hid_dsm_fn_mask & BIT(fn_index)))
 		goto skip_dsm_exec;
 
 	/* All methods expects a package with one integer element */
@@ -214,7 +214,19 @@ static void intel_hid_init_dsm(acpi_handle handle)
 	obj = acpi_evaluate_dsm_typed(handle, &intel_dsm_guid, 1, 0, NULL,
 				      ACPI_TYPE_BUFFER);
 	if (obj) {
+		switch (obj->buffer.length) {
+		default:
+		case 2:
+			intel_hid_dsm_fn_mask = *(u16 *)obj->buffer.pointer;
+			break;
+		case 1:
 			intel_hid_dsm_fn_mask = *obj->buffer.pointer;
+			break;
+		case 0:
+			acpi_handle_warn(handle, "intel_hid_dsm_fn_mask length is zero\n");
+			intel_hid_dsm_fn_mask = 0;
+			break;
+		}
 		ACPI_FREE(obj);
 	}